A thermal imager or forward looking infrared (FLIR) system is a passive system that does not transmit radiation into a sector being observed or scanned, but instead detects infrared energy emanating from the target scene. The FLIR sensitivity allows it to function as a thermal sensing surveillance system for observing objects of interest at long range whether or not visibility is good or poor. FLIR capability, therefore, enables forces to observe actions of others or opposing forces without transmitting a tell-tale signal toward the opposing forces. However, when opposing forces determine that they are being observed, various steps can be taken to destroy or cripple the FLIR capability if desired. It is known that relatively concentrated laser energy, directed into a FLIR during momentary alignment between the FLIR optical axis and the laser, can damage the FLIR's optics and/or detector cells and thereby incapacitate the system. Accordingly, testing a passive FLIR, by subjecting it to pulses of energy from a remote laser, allows several factors to be determined such as the minimum amount of laser energy necessary to incapacitate the FLIR, the degree of damage at various incremental angles of incidence away from coincidence, counter measures that can be taken to reduce damage to friendly FLIR's, and measures that can be taken to increase the damage to unfriendly FLIR's To this end a scan synchronizer and pulsing system is set forth that allows precise and controllable triggering of laser pulses toward a FLIR during adjustable time periods.